Isotopes of an element have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have a different total number of nucleons (different mass number), which is the number of protons plus neutrons. Different isotopes of a given element all have the same number of protons and electrons, and therefore the same electronic structure.
Thus the physical and chemical properties of different isotopes are very similar. But isotopically pure components can be very useful in industry because they show slightly different properties. For example, isotopically pure 28Si can be used to solve heat problems in high performance silicon chips. 13C is commonly used in research science and medicine.
There is a need to develop efficient methods for separation of isotopes. Since isotopes have very similar chemical properties, sophisticated processes have been set up. For example, some processes are based on diffusion, centrifugal effect, electromagnetic, laser, chemical exchange, gravity, or chromatography.
The US Patent Application no 2005/0247195 discloses a method for separation of isotopes, where a specific isotope of an isotope composition is purified by exploiting the difference in the isotope's mass diffusivity by making the natural isotope composition, in one cycle, travel in a mass stream through a media by diffusion and optionally also convection, and thus obtain a fractioning of the isotopes such that the wanted isotope is enriched in one fraction of the mass stream, collecting this enriched fraction of the mass stream and sending it through another cycle to obtain a fraction with higher content of the wanted isotope, and repeat these cycles until the wanted isotope has become sufficiently enriched, characterised in that the hydrogen is used as ligand on the element that is to be separated, and that the hydrogen and the element that is to be separated is employed in the form of a chemical compound that is in a gaseous state at the actual pressure and temperature, and that the gaseous hydrides are separated by mass diffusion through a chromatographic column. However, the method needs several stages before obtaining the required purity.